Last fall, the rumors leading up to the iPad mini event suggested that the 8-inch tablet would have a microphone located in the top-middle of its rear shell. Just like on the iPhone 5, it was to be used for noise-canceling and to improve audio pickup.

Obviously, the rumors never materialized, as the production version of the first-gen mini does not have a hole in the top of its rear casing. But looking at some new pictures of a purported prototype for the slate, that may not have been Apple’s plan…

Sonny Dickson, who has provided accurate intel and photos of leaked components in the past, writes:

“According to our sources, Apple had originally planned to incorporate what appears to be a second microphone in the recent version of the iPad mini.

The photos show the prototype iPad mini with an extra hole centered, atop the rear of the device. It is unclear as to why Apple withheld the second microphone from the final product release, my guesses would be that it was axed out to cut down on cost, or to be preserved for a future generation iPad mini.”

The prototype is interesting for a few reasons. For one, it validates the reports that claimed the iPad mini would have a rear mic—Apple must have decided to pull it at the last minute. And two, it explains all of those mini cases with the holes in their backs.

Though the first generation iPad mini didn’t actually get the rear mic, both the iPhone 5 and current-gen iPod touch have them. And the word is that the iPad 5 will have one located right next to its rear camera, so we imagine the next-gen mini will too.

If nothing else, it’s always cool to see Apple’s prototype devices in the light. Dickson says that typically, prototypes are stolen by Foxconn workers and sold to Chinese case manufactures for a price in upwards of 38,000 RMB, or about $6000 USD.